In the case of high-capacity direct-current arc furnaces, the high currents flowing in the current lead-in and lead-off lines give rise to deflections of the arc. The arc does not burn vertically. Rather, the arc is directed towards the furnace wall and gives rise to overheating there.
As a result of a particular arrangement of the current feed and discharge lines underneath and next to the furnace vessel, a "centering" of the arc can be obtained. Thus, in U.S. Pat. No. 4,550,413 and U.S. Pat. No. 4,577,326 it is proposed to lay these lines in such a way that the magnetic fields caused by the flowing direct current act on the arc symmetrically. These measures are expensive, however, and increase not only the cost but also the space requirement of the furnace. Another solution consists in making the electrode together with the electrode support apparatus horizontally displaceable relative to the furnace vessel in order thereby to compensate for asymmetries in the current feed and discharge. This measure is also very expensive, because sufficient space has to be provided in the furnace cover for the movement path of the electrode.
Whereas the current feed gives rise to undesired deflection of the arc, it may well be the case in practice that the arc is to be deflected intentionally in one direction or another in order, for example in the region of an eccentric bottom taphole or in the case of furnaces with continuous charging, to produce more heat in said regions. This would only be possible by horizontal movement of the electrode relative to the furnace vessel, which would however be very expensive.